I was comparing different caching techniques using MTRR entries and I found something strange. Note the output is from a basic utility that uses mmap.
NV Memory: Write-back Writes took 2075.993408 Megabytes per second Reads took 2130.842529 Megabytes per second No Errors Found Write-Through Writes took 55.332256 Megabytes per second Reads took 92.310310 Megabytes per second No Errors Found !!!I was expecting this number to be the same as Write-back Uncached Writes took 55.331089 Megabytes per second Reads took 92.315132 Megabytes per second No Errors Found Regular memory: Write-back Writes took 1875.560791 Megabytes per second Reads took 2070.452637 Megabytes per second No Errors Found Write-Through Writes took 54.903713 Megabytes per second Reads took 2106.244629 Megabytes per second No Errors Found !!!This is what I expected to see for NV Memory Uncached Writes took 54.903923 Megabytes per second Reads took 90.150986 Megabytes per second No Errors Found I am using the same driver (which adds MTRR entries to change caching type) there is no physical reason why write through should behave differently when using NV Memory. Does anybody on this mailing list who may be more familiar with caching techniques know why this might me the case? Brian -- CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina Corporation (or any of its subsidiaries), or any other person or entity. _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
